Gas blast circuit breaker of the axial blast type with magnetic means for rotating an arc terminal



J. w BEATTY 3,274,365 GAS BLAST CIRCUIT BREAKER OF THE AXIAL BLAST TYPESept. 20, 1966 WITH MAGNETIC MEANS FOR ROTATING AN ARC TERMINAL FiledAug. 16, 1963 2 Sheets-Sheet 1 INVENTOR. JOHN WBEATTY,

5 ATTORNEY.

GAS BLAST CIRCUIT BREAKER OF THE AXIAL BLAST TYPE WITH MAGNETIC MEANSFOR ROTATING AN ARC TERMINAL Filed Aug. 16, 1963 Se t. 20, 1966' J. w.BEATTY 2 Sheets-Sheet INVENTOR. JOHN W BEATTY,

BY ATTORNEY.

United States Patent GAS BLAST CIRCUIT BREAKER OF THE AXIAL BLAST TYPEWlITH MAGNETIC MEANS FOR ROTATING AN ARC TERMINAL John W. Beatty,Newtown Square, Pa, assignor to General Electric Company, a corporationof New York Filed Aug. 16, 1963, Ser. No. 302,613 8 (Ilaizns. (Cl.200-148) This invention relates to a gas blast circuit breaker of theaxial blast type and, more particularly, to means for improving theinterrupting ability of such a circuit breaker.

The usual gas blast circuit breaker comprises means for establishing anelectric arc across a gap between two electrodes and means for directinga high velocity blast of gas into the arcing region. The purpose of thegas blast is to cool the arc and to scavenge the arcing region of arcingproducts so as to increase the rate at which dielectric strength isbuilt up across the gap when the current zero point is reached. Byincreasing this rate of dielectric recovery, it is possible to improvethe ability of the gap to withstand the usual recovery voltage transientwhich builds up as soon as current zero is reached, thus improving theinterrupting ability of the circuit breaker.

In an axial blast type of circuit breaker, there is typically providedan orifice through which the are between the electrodes extends andthrough which the gas blast flows axially of the are about the peripheryof the arc. The purpose of the orifice is to guide the blast withrespect to the arc and to impart the desired high velocity to the blast.The electrode that is located upstream from the orifice is referred tohereinafter as the upstream electrode, and the electrode that is locateddownstream from the orifice is referred to hereinafter as the downstreamelectrode.

A typical axial blast circuit breaker is so designed that the gas blastforces the are into a stable position where it is held captive untilextinguished at a current zero. Any tendency of the arc to move out ofthis stable position is counteracted by relatively high aerodynamicforces on the arc resulting from the gas blast.

It has been proposed heretofore to improve the interrupting ability 'ofa circuit breaker by magnetically moving the are so as to promotecooling, but such magnetic are moving schemes have largely been limitedto circuit breakers in which the arc is not held captive by a highvelocity blast of fluid, and therefore such schemes have not generallybeen used in the axial blast type of gas blast circuit breaker. Magneticare moving schemes have largely been ignored for this axial blast typeof breaker primarily because it has geen generally thought that themagnetic rforces developed by any practical magnetic arrangement wouldbe so small in comparison to the large aerodynamic forces prevailingthat such magnetic means would serve no useful purpose.

An object of my invention is to incorporate magnetic arc moving meansinto an axial gas blast circuit breaker in such a manner as to improveits rate of dielectric recovery when the current zero point is reached.

Another object is to incorporate arc rotating means into an axial blastcircuit breaker in such a manner that the arc rotating means is capableof rotating the upstream terminal of the arc for all positions that thisterminal may reach while held captive within the aerodynamicallystagnant region adjacent the upstream electrode.

In the disclosed circuit breaker, the downstream terminal ocE the arc isheld captive within a stagnation region upstream from the downstreamelectrode and is thus prevented from moving further downstream, where itcould damage various sensitive parts of the circuit breaker. Anotherobject is to produce the desired arc rotation without 3,274,365 PatentedSept. 20, 1966 dislodging the downstream terminal of the are from itscaptive relationship with the downstream electrode.

In carrying out my invention in one form, I provide a gas blast circuitbreaker of the axial blast type that comprises a downstream electrodeand an upstream electrode between which an arc is established. Anorifice is provided about the region in which the arc is located whenpresent between the electrodes. Means is provided for causing a blast ofpressurized gas to flow at high speed about the upstream electrode andthrough the orifice axially of the are about the arc periphery towardthe down stream electrode. This axial blast of gas envelopes theupstream electrode and establishes a stagnation zone, or wa'ke, on thedownstream side of the upstream electrode. The aerodynamic forcesresulting from this gas blast force the upstream arc terminal into thisstagnation zone. I rotate the upstream arc terminal within thestagnation zone by applying a radial magnetic held to the arc in theregion of the upstream electrode. There is a central region disposedwithin the stagnation zone in which the radial magnetic field is weakand has little arc rotating capability, but I provide means :forpreventing entry of the upstream arc terminal into this central regionso that the arc is continuously rotated while within the stagnationzone. This rotation of the arc within the stagnation zone has resultedin substantial improvements in the rate of dielectric recovery atcurrent zero. Although the gas blast can ordinarily apply relativelyhigh aerodynamic forces to the arc; in the stagnation zone theseaerodynamic forces are relatively low and the magnetic means cantherefore produce significant motion of the arc.

For a better understanding of my invention, reference may be had to theEfOllOWing description taken in conjunction with the accompanyingdrawings, wherein:

FIG. 1 is a sectional View of a gas blast circuit interrupter embodyingone form of my invention.

FIG. 2 is an enlarged sectional view of the upstream electrode of thecircuit interrupter Olf FIG. 1.

FIG. 3 is a sectional view of a modified form of up stream electrode.

FIG. 4 is a plan view of another modified form of upstream electrode.

FIG. 5 is an end view of the electrode of FIG. 4.

Referring now to FIG. 1, the circuit interrupter shown therein is of thesustained-pressure, gas-blast type described and claimed in my US.Patent No. 2,783,338, assigned to the assignee of the present invention.Only those parts of the interrupter that are considered necessary toprovide an understanding of the present invention have been shown inFIG. 1. In this respect, only the right hand port-ion of the interrupterhas been shown in section inasmuch as the interrupter is generallysymmetrical wi-th respect to a vertical plane and the left hand portionis substantially identical to the right hand portion. As described indetail in my above-mentioned patent, the interrupter comprises a casing12 which is normally filled with pressurized gas to define aninterrupting chamber 11. Located within the interrupting chamber 11 area pair of relatively movable contacts 14 and 16 which can be separatedto draw an are within the pressurized gas within the chamber 11. Thecontact 14 is relatively stationary, whereas the other contact 16 ismounted for pivotal motion about a fixed, current carrying pivot 18.When the movable contact 16 is driven clockwise about the pivot 18 fromits solid-line closed position of FIG. 1, an arc is established in theregion where the contacts part. The movable contact 16 is shown bydotted lines in FIG. 1 in a partially open position through which itpasses during a circuit interrupting operation after having establishedan arc.

The movable contact 16 is supported by means of its current carryingpivot 18 on a conductive bracket 19 that is preferably formed integralwith a stationary cylinder 32. The cylinder 32 at its lower end issuitably supported from a generally cylindrical casting 33. The casting33 at its lower end is suitably secured to a flange 35 rigidly carried.by the stationary metallic casing 12.

For producing a gas blast to aid in extinguishing the arc, thecylindrical cast'ing 33 contains a normally closed exhaust passage 36leading from the interrupting chamber 11 to the surrounding atmosphere.The casting 33 at its upper end is provided with a tubular nozzle typeelectrode 38 having an orifice portion 39 at its outer end defining aninlet 37 to the exhaust passage 36. This inlet 37 is referred tohereinafter as the orifice opening. The how of arc extinguishing gasthrough the tubular nozzle 38 and the exhaust passage 36 is controlledby means of a cylindrically-shaped reciprocable blast valve member 40located at the outer, or lower, end 'of the exhaust passage 36. Thisblast valve member 40 normally occupies a solid-line, closed positionwherein an annular flange 42 formed at its lower end sealingly abutsagainst a stationary valve seat 34 carried by the exhaust casting 33.

During a circuit interrupting operation, the movable blast valve member40 is driven upwardly from its solid line, closed position of FIG. 1through a partially open intermediate position shown in dotted lines inFIG. 1. Opening of the valve member 40 allows pressurized gas in thechamber 11 to how at high speed through the orifice opening 37 andnozzle 38 and out the exhaust passageway -36 past the valve member 40 toatmosphere, as indicated by the dot-ted line arrows B of FIG. 1. Themanner in which the gas blast acts to extinguish the arc will soon bedescribed in greater detail.

At its upper end, the cylindrical valve member 40 surrounds atprojecting tubular support 41 upon which the valve member 40 is smoothlyslidable. The tubular support 41 is fixed to the casting 3'3,preferably, by means of bolts (not shown) clamping the flange 41a to thetop of casting 33. A compression spring 44 positioned between themovable valve member 40 and the lower end of support 41 tends to holdthe valve member 40 in its closed position against the valve seat 34.

To protect the support 41 and the upper end of the valve member 40 fromthe harmful effects of arcing, a protective metallic tube 43 ispositioned about these parts and is suitably secured to the support 41.Secured to the outer surface of this tube is a downstream probe orelectrode 45, preferably of a refractory metal, which projects radiallyfrom the tube 43 and transversely into the path of the gas blast flowingthrough the passageway 36. As will soon appear more clearly, thedownstream terminal of the arc is transferred to this electrode 45during an interrupting operation and, after such transfer, occupies aposition generally corresponding to that shown at 46. The downstreamelectrode is preferably constructed as shown and claimed in Patent No.2,897,324, Schneider, assigned to the assignee of the present invention,so that it has a nonstreamlined upstream surface 48 that coacts with thegas blast to form a stagnation region upstream from the surface 48. Theterminal of an are such as 46 reaching the electrode 45 is capturedwithin the stagnation region and thus prevented from being drivenfurther downstream by the gas blast.

For controlling the operation of the movable blast valve 40 and movablecontact 16, a combined operating mechanism 50 is provided. Thismechanism 50 is preferably constructed in the manner disclosed andclaimed in my aforementioned Patent 2,783,338, and its details form nopart of the present invention. Generally speaking, this mechanism 50comp-rises a valve controlling piston 51 and a contact-controllingpiston 52 mounted within the cylinder 32. The valve controlling piston51 is coupled to the movable valve member 40 through a piston rod 54suitably clamped to the valve member 40. The contact controlling piston52, on the other hand, is connected to the movable contact 16 through apiston rod 58 and a cross head 59 secured to the piston rod. A link 60pivotally joined to the cross head 59 at 61 and to the movable contact16 at 62 interconnects the cross head 59 and the movable contact 16.When the valve controlling piston 51 is driven upwardly, it acts to openthe vlave member 40, and, simultaneously, to drive thecontact-controlling piston 52 upwardly to produce opening movement ofthe movable contact member 16.

Opening movement of the contact member 16 first establishes an arebetween the ends of the contacts 14 and 16. Shortly thereafter, however,the blast of gas which has been flowing through the orifice opening 37,as indicated by the dotted line arrows B, forces the upstream terminalof the are on to an upstream arcing electrode 70, which is electricallyconnected to the stationary contact 14. As opening motion of the movablecontact 16 continues, the gas blast forces the downstream terminal ofthe arc to transfer from the movable contact 16 to orifice structure 39,which is electrically connected to the movable contact 16. The gas blastthen impels the downstream terminal of the arc through the orificeopening 37 and nozzle 38 on to the upper end of the protective metallictube 43. From there, the gas blast drives the downstream arc terminaldownwardly and into the previously described stagnation region adjacentthe upstream surface 48 of the electrode 45. The arc then occupies theposition generally shown in 46. When the arc is in this position, thearc column extends through the orifice opening 37 and is subjected inthe orifice region to an intense high velocity blast that extendsaxially of the arc. This axial blast is effective to cool and deionizethe arc and scavenge the arcing region of arcing products, thuspreventing reignition thereof at an early current zero. The downstreamelectrode 45 and the upstream electrode 70 are so located that thelength of the arc and the position of the are are at optimum values tofacilitate high speed arc-extinction. In other words, this is theposition of the arc in which it is most vulnerable to extinction.

It is generally understood that the ability of a circuit breaker toprevent the arc from reigniting at a current zero depends upon the rateat which dielectric strength is recovered across the arcing region whenarcing ceases at the current zero. The faster the dielectric recoveryrate, the lower the chances for reignition and thus the better thechances for successful interruption at this point.

I have found that substantial improvements in this dielectric recoveryrate can be made by rotating the upstream terminal of the are about acentral point on the downstream face of the upstream electrode 70. Themagnetic force for rotating the arc is derived from a coil electricallyconnected in series with the electrode 70 and located behind thedownstream face of the electrode 70. This coil 80 encircles a conductivestud 82 which carries current to and from the upstream electrode. Theleft hand end of the coil 80 is electrically connected to the free endof the stud 82, and the right hand end of the coil is electricallyconnected to the electrode 70 at the rear end of the electrode 70.Suitable insulation 72 assures that current flowing through theelectrode '70 will not bypass the coil 80 or any of its turns.

The electrode 70 is a cup-shaped member having an end cap 84 at its rearend to which the right hand end of the coil 80 is connected. Theelectrode 70 comprises a tubular wall portion 85 surrounding the coil 80and a convex forward portion, or base portion, 86 of an arcresist-antrefractory metal brazed to the tubular wall portion. The forward portion86 has a centrally disposed opening 87 located therein, and the tubularwall 85 has openings 88 extending radially therethrough andcommunicating with the central opening 87. When the blast valve 40 ofthe circuit breaker is opened, as was described hereinabove, pressurizedair not only flows into the orifice 39 via paths such as B but also viapaths that extend radially inwardly through the openings 88 and thenaxially of the electrode 70 and out through the centrally disposedopening 87. This auxiliary blast of air through the opening 87 helps toprevent the arc terminal from entering the central opening 87 andfinding a possible stable footing therein.

When the upstream are terminal is transferred from the stationarycontact 14 to the electrode 70, as was described hereinabove, it isforced by the main air blast enveloping the electrode 70 to move towardthe forward end of the electrode. Current is then flowing through thecoil 80 since the coil is connected in series with the arc. This currentflowing through the coil 80 produces a magnetic field that extendsgenerally radially with respect to the central opening 87 of theelectrode in the region of the forward portion 86 of the electrode. Theapproximate configuration of this magnetic field is generallyillustrated by the dotted lines of force M, which extend radiallyoutward from the central opening 87 adjacent the electrode 70. Thisradial magnetic field reacts in a known manner with the local fieldsurrounding the arc to produce a circumferentially acting magnetic forcethat rotates the upstream arc terminal about the central opening 87.

Magnetic arc rotating arrangements have heretofore largely been ignoredfor axial blast types of air blast circuit breakers, primarily becauseit has been generally thought that the magnetic forces developed by anypractical magnetic arrangement would be so small in comparison to thelarge aerodynamic forces prevailing in such a breaker that such magneticmeans would serve no useful purpose. This thinking, however, hasoverlooked the important fact that, even though the gas blast istraveling at high velocity past the electrode, the arc terminal can belocated in a stagnation region in which the aerodynamic forces on theare are relatively low. When the arc terminal is in such a zone of lowaerodynamic force, a relatively small magnetic force on the arc can be asignificant factor in moving the arc terminal. With the illus tratedelectrode 70, there is such a stagnation zone in the region immediatelysurrounding the central opening 87 of the electrode 70. This stagnationzone is designated 90 in FIG. 2. In this region the gas is moving at lowvelocity in large scale eddies such as illustrated by the closed loops91. The air blast following the paths B will force the upstream arcterminal into this stagnation zone, where it will be held captive by theflow stream bounding the stagnation region. While the upstream arcterminal is captured in this manner in the stagnation zone 90, theradial magnetic field will rotate the upstream arc terminal about thecentral opening 87, as was described hereinabove.

It is important to note that the upstream arc terminal is excluded fromthe central region of the upstream electrode. The reason for this isthat in the central region, the magnetic field resulting from currentthrough the coil 80 has virtually no radial component. The direction ofthe field is almost entirely axial in the central region. Thus, themagnetic field would have little or no ability to rotate any are thatmight have its terminal located in the central region. This being thecase, the improvements obtainable from are rotation would be largelynullified if the arc terminal were permitted to hang in this region. Thefact that this central region contains an opening 87 and particularly anopening through which a blast of air is flowing prevents the are fromhanging in this region and thus preserves the effectiveness of the arcrotating arrangement.

FIG. 3 illustrates an alternative approach for excluding the upstreamterminal of the are from the region at the center of the upstreamelectrode. In this embodiment, a central opening 87 is provided in thecentral region of the electrode but instead of defining a flow passage,this central opening is filled with an insert of arc resistantinsulating material. A suitable insulating material for this insert ispolytetrafluoroethylene, sold under the trade name of Teflon. Sincethere is no conductive metal in the central reg-ion to which the arcterminal can attach, it remains in the portion of the stagnation zoneradially outside of the insulating insert 100. The upstream electrode ofFIG. 3 is otherwise essentially the same as the electrode depicted inFIGS. 1 and 2, and corresponding reference numerals have been used todesignate corresponding parts in the two embodiments.

It is to be noted that the upstream electrode 70 is of a hollowconstruction and that the current path through the electrode to ,or fromany are terminal on the electrode extends from the arc terminal to therear end of the electrode. This current path together with the currentpath leading through an are on the electrode forms a loop which bows inthe direction of the stagnation region whenever the arc terminal islocated on the electrode at a point outside the stagnation region. Thisdesirably aids in moving the arc terminal int-o the stagnation region,where it can be rotated as described hereinabove. When the arc terminalis in the stagnation region, the loop ordinarily tends to force theterminal toward the center of the stagnation region where the arcrotating force is low. But the auxiliary blast in FIG. 2 and theinsulating insert in FIG. 3 prevent the arc from reaching the center andthus assure the desired arcrotation.

It is to be noted that my arc rotating means is confined to a locationimmediately adjacent the upstream terminal of the are. Due to thislocation, the magnetic field M has a relatively strong radial componentonly in the region immediately adjacent the upstream electrode. Atlocations further downstream, this radial component of magnetic force isrelatively weak. Thus the radial magnetic field acts primarily upon theportion of the are immediately adjacent the upstream electrode.Accordingly, there is little tendency for the radial magnetic field tomove the downstream arc terminal out of its captive location adjacentthe downstream electrode. This is advantageous because if the downstreamterminal were permitted to move out of its captive relationship it couldbe driven further downstream by the gas blast and possibly cause damageto vital parts of the circuit breaker.

FIG. 4 shows a modified form of upstream electrode 70 correspondinggenerally to that of FIG. 2 but differing therefrom in that slots 107and an insert of are resistant refractory metal are provided in theelectrode. The insert 105 is disposed in angular alignment with theforward end of stationary contact 14, and thus the insert is in aposition to receive the upstream arc terminal when this terminal istransferred on to the upstream electrode. This insert 105 provides apath for the upstream arc terminal leading from a point where the arcterminal first attached to the electrode 70 to the forward portion 86 ofthe electrode. A preferred material for the insert 105 is acopper-tungsten mixture, sold under the trade name of Elkonite; theremainder of the tubular wall portion 85 of the upstream electrode ismade of a highly conductive but less refractory material, such ascopper.

The slots 107 have their long dimension extending longitudinally of thetubular wall portion 85 of the electrode, and a pair of adjacent slotsborder the insert 105. These slots also extend through the entire radialthickness of the wall portion 85. The purpose of the slots 107 is toforce most of the current that flows through the electrode 70 to an arcterminal on the insert 105 to follow paths such as 110 which approachthe are solely through the insert 105 and from the back of theelectrode. By forcing the current to follow such paths, a more definiteloop bowing toward the forward face of the electrode is defined by theoverall current path leading through the arc and the paths 110. Thisresults in a greater magnetic force urging the arc toward the forwardface of the electrode. In addition, the slots 107 tend to block the flowof current to the arc terminal through paths that extendcircumferentially of the electrode 70 and thus reduce the tendency ofthe arc to move circumferentially of the electrode until it reaches theforward face 86 of the electrode. By forcing the arc to move quickly tothe forward face 86 of the electrode 70 by a path that is confined tothe are resistant insert 105, the exposure of the less refractoryportions of the electrode to the arc is substantially reduced and thepossibilities for excessive arc-erosion are reduced.

While I have shown and described particular embodiments of my invention,it will be obvious to those skilled in the art that various changes andmodifications may be made without departing from my invention in itsbroader aspects, and I, therefore, intend in the appended claims tocover all such changes and modifications as fall within the true spiritand scope of my invention.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

1. An electric circuit breaker of the axial-blast, gasblast typecomprising:

(a) a pair of electrodes between which an arc is estab lished duringcircuit interruption,

(b) an orifice having an opening through which said are is adapted toextend when present between said electrodes,

(c) means for causing a stream of gas to pass through said orificeopening axially of the are about the periphery of said are,

((1) portions of said gas stream flowing closely adjacent to the outerperiphery of the electrode located upstream from said orifice butseparating from the surface of said electrode in a region facing theorifice opening, whereby to define a stagnation zone in said latterregion,

(e) said are having an upstream terminal that is held captive in saidstagnation zone during a circuit interrupting operation,

(f) magnetic means for rotating said upstream terminal about a point onsaid upstream electrode while said upstream arc terminal is held captivein said stagnation zone,

(f) said upstream electrode comprising a generally cup-shaped membersurrounding said magnetic means with the base of said cup-shaped memberfacing downstream with said stagnation zone positioned on said base,means for forcing current flowing through said cup-shaped member to anarc terminal in said stagnation zone to flow from the outer periphery ofsaid cup-shaped member radially inwardly, thereby developing aradially-inwardly acting magnetic force on said arc to help hold the arcin said stagnation zone.

(g) said cup-shaped member having a central region of said base disposedwithin said stagnation zone in which said magnetic means has relativelyweak arc rotating abilities,

(h) and means for preventing entry of said upstream arc terminal intosaid central region.

2. The electric circuit breaker of claim 1 in which the means forpreventing entry of said upstream arc terminal into said central regioncomprises means for causing an auxiliary blast of gas to flow throughsaid central region toward said orifice opening.

3. The electric circuit breaker of claim 1 in which the means forpreventing entry of said upstream arc terminal into said central regioncomprises electrical insulating material located in said central region.

4. The interrupter of claim 1 in which said magnetic means produces anarc rotating force that is relatively strong in the region adjacent theupstream terminal of the arc and is relatively weak in the regionadjacent the downstream terminal of the arc, and means for holding thedownstream terminal of said are generally stationary on the downstreamone of said electrodes while the upstream terminal of said are is beingrotated.

5. An electric circuit breaker of the axial blast, gas

blast type comprising:

(a) a pair of electrodes between which an arc is established duringcircuit interruption,

(b) means for causing a stream of gas to flow axially of said arc aboutthe periphery thereof,

(c) portions of said gas stream flowing closely adjacent to the upstreamone of said electrodes but separating from the surface of said electrodeat the downstream face thereof, whereby to define a stagnation zone atsaid downstream face,

(d) said are having an upstream terminal that is held captive in saidstagnation zone during a circuit-interrupting operation,

(e) said upstream electrode comprising a forward portion having asurface defining said downstream face and a tubular wall portionextending from said forward portion in a direction upstream therefrom,

(f) said forward portion being of an arc resistant refractory metal andmost of said wall portion being of a less refractory metal,

(g) said wall portion having a predetermined region upstream from saidstagnation zone where said upstream terminal first attaches to saidupstream electrode,

(h) an insert of are resistant refractory metal in said wall portiondefining a path extending between said predetermined region and saidforward portion to provide a path for the upstream arc terminal tofollow in entering said stagnation zone,

(i) said wall portion containing slots circumferentiallyspaced aroundsaid electrode and having their long dimension extending in a directionlongitudinally of said wall portion to restrict the circumferential flowof current through said electrode, and

(j) an adjacent pair of said slots bordering said arcresistant insert.

6. An electric circuit breaker of the axial-blast, gas

blast type comprising:

(a) an upstream and a downstream electrode between which an arc isestablished during circuit interruption,

(b) an orifice having an opening through which said arc is adapted toextend when present between said electrodes,

(c) means for causing a stream of gas to pass through said orificeopening axially of the arc about the periphery of said arc,

(d) portions of said gas stream flowing closely adjacent to the outerperiphery of said upstream electrode but separating from the surface ofsaid upstream electrode in a region facing the orifice opening, wherebyto define a stagnation zone in said latter region,

(e) said are having an upstream terminal that is held captive in saidstagnation zone during a circuit interrupting operation,

(f) and magnetic means for rotating said upstream terminal about a pointon said upstream electrode while said upstream arc terminal is heldcaptive in said stagnation zone,

(f) said upstream electrode comprising a generally cup-shaped membersurrounding said magnetic means with the base of said cup-shaped memberfacing downstream with said stagnation zone positioned on said base,means for forcing current flowing through said cup-shaped member to anarc terminal in said stagnation zone to flow from the outer periphery ofsaid cup-shaped member radially inwardly, thereby developing aradially-inwardly acting magnetic force on said are to help hold the arcin said stagnation zone,

(g) said cup-shaped member having a central region of said base disposedwithin said stagnation zone in which said magnetic means has relativelyweak arc rotating abilities,

(h) and means for preventing entry of said upstream arc terminal intosaid central region,

(i) said magnetic means being confined to a location immediatelyadjacent said upstream electrode so as to produce an arc rotatingmagnetic field that is relatively strong in the region adjacent saidupstream arc terminal and is relatively weak in the region adjacent thedownstream arc terminal,

(j) and means for holding the downstream terminal of said arc generallystationary on said downstream electrode while said upstream terminal isbeing rotated.

7. An electric circuit breaker of the axial blast, gas

blast type comprising:

(a) a pair of electrodes between which an arc is established duringcircuit interruption,

(b) an orifice having an opening through which said are is adapted toextend when present between said electrodes,

(c) means for causing a stream of gas to pass through said orificeopening axially of the arc about the periphery of said are,

(d) portions of said gas stream flowing closely adjacent to theelectrode located upstream from said orifice but separating from thesurface of said electrode in a region facing the orifice opening,whereby to define a stagnation zone in said latter region,

(e) said arc having an upstream terminal that is held captive in saidstagnation zone during a circuit interrupting operation,

(f) magnetic means for rotating said upstream terminal about a point onsaid upstream electrode while said upstream arc terminal is held captivein said stagnation zone,

(g) said upstream electrode having a central region disposed within saidstagnation zone in which said magnetic means has relatively weak arcrotating abilities,

(h) and means for preventing entry of said upstream arc terminal intosaid central region,

(i) said upstream electrode comprising a forward portion that is locatedwithin said stagnation zone and a tubular wall portion extending fromsaid forward portion in a direction upstream therefrom.

(j) said forward portion being of an are resistant refractory metal andmost of said Wall portion being of a less refractory metal,

(k) said wall portion having a predetermined region upstream from saidstagnation zone where said up stream arc terminal first attached to saidupstream electrode,

(1) an insert of arc-resistant refractory metal in said wall portiondefining a path extending between said predetermined region and saidforward portion to provide a path for the upstream arc terminal tofollow in entering said stagnation zone.

(m) said wall portion containing slots circumferentially spaced aboutsaid electrode and having their long dimension extending in a directionlongitudinally of said wall portion to restrict the circumferential flowof current through said electrode, and

(11) an adjacent pair of said slots bordering said arcresistant insert.

8. An electric circuit breaker of the axial blast, gas

blast type comprising:

(a) a pair of electrodes between which an arc is established duringcircuit interruption,

(b) an orifice having an opening through which said are is adaptedtoextend when present between said electrodes,

(c) means for causing a stream of gas to pass through said orificeopening axially of the arc about the periphery of said arc,

fine a stagnation zone in said latter region,

terrupting operation,

(f) magnetic means for rotating said upstream terminal about a point onsaid upstream electrode while said upstream arc terminal is held captivein said stagnation zone,

(g) said upstream electrode having a central region disposed within saidstagnation zone in which said magnetic means has relatively weak arcrotating abilities,

(h) and means for preventing entry of said upstream arc terminal intosaid central region,

(i) said upstream electrode being of a hollow construction and saidmagnetic means comprising a coil located within said hollow electrode,

(j) a conductive stud projecting into said hollow upstream electrodefrom the back thereof for supporting said electrode and for carryingcurrent to and from said electrode, and

located upstream from said stagnation zone.

References Cited by the Examiner 9 UNITED STATES PATENTS ReferencesCited by the Applicant UNITED STATES PATENTS 1/1936 Rankin et al.2,051,478 8/ 1936 Hampton et al. 2,897,324 7/ 1959 Schneider.

60 ROBERT K. SCHAEFER, Primary Examiner.

ROBERT S. MACON, KATHLEEN H. CLAFFY,

Examiners.

P. E. CRAWFORD, Assistant Examiner.

(e) said are having an upstream terminal that is held captive in saidstagnation zone during a circuit in- (k) said coil encircling said studand being connected at one end to the forward end of said stud and atits opposite end to a portion of said electrode Rankin et a1 200147 XHampton et al 200144 Slepian 200147 Rankin 200-144 X Strom 200147 XSchneider 200148

1. AN ELECTRIC CIRCUIT BREAKER OF THE AXIAL-BLAST, GASBLAST TYPECOMPRISING: (A) A PAIR OF ELECTRODES BETWEEN WHICH AN ARC IS ESTABLISHEDDURING CIRCUIT INTERRUPTION, (B) AN ORIFICE HAVING AN OPENING THROUGHWHICH SAID ARC IS ADAPTED TO EXTEND WHEN PRESENT BETWEEN SAIDELECTRODES, (C) MEANS FOR CAUSING A STREAM OF GAS TO PASS THROUGH SAIDORIFICE OPENING AXIALLY OF THE ARC ABOUT THE PERIPHERY OF SAID ARC, (D)PORTIONS OF SAID GAS STREAM FLOWING CLOSELY ADJACENT TO THE OUTERPERIPHERY OF THE ELECTRODE LOCATED UPSTREAM FROM SAID ORIFICE BUTSEPARATING FROM THE SURFACE OF SAID ELECTRODE IN A REGION FACING THEORIFICE OPENING, WHEREBY TO DEFINE A STAGNATION ZONE IN SAID LATTERREGION, (E) SAID ARC HAVING AN UPSTREAM TERMINAL THAT IS HELD CAPTIVE INSAID STAGNATION ZONE DURING A CIRCUIT INTERRUPTING OPERATION, (F)MAGNETIC MEANS FOR ROTATING SAID UPSTREAM TERMINAL ABOUT A POINT ON SAIDUPSTREAM TERMINAL THAT IS HELD SAID UPSTREAM ARC TERMINAL IS HELDCAPTIVE IN SAID STAGNATION ZONE, (F'') SAID UPSTREAM ELECTRODECOMPRISING A GENERALLY CUP-SHAPED MEMBER SURROUNDING SAID MAGNETIC MEANSWITH THE BASE OF SAID CUP-SHAPED MEMBER FACING DOWNSTREAM WITH SAIDSTAGNATION ZONE POSITIONED ON SAID BASE, MEANS FOR FORCING CURRENTFLOWING THROUGH SAID CUP-SHAPED MEMBER TO AN ARC TERMINAL IN SAIDSTAGNATION ZONE TO FLOW FROM THE OUTER PERIPHERY OF SAID CUP-SHAPEDMEMBER RADIALLY INWARDLY, THEREBY DEVELOPING A RADIALLY-INWARDLY ACTINGMAGNETIC FORCE IN SAID ARC TO HELP HOLD THE ARC IN SAID STAGNATION ZONE.(G) SAID CUP-SHAPED MEMBER HAVING A CENTRAL REGION OF SAID BASE DISPOSEDWITHIN SAID STAGNATION ZONE IN WHICH SAID MAGNETIC MEANS HAS RELATIVELYWEAK ARC ROTATING ABILITIES, (H) AND MEANS FOR PREVENTING ENTRY OF SAIDUPSTREAM ARC TERMINAL INTO SAID CENTRAL REGION.